Thermophilic Anaerobic Treatment of Cassava Ethanol Wastewater in Continously Stirred Tank Reactor (CSTR)

The high content of organic matter and suspended solids with relatively low pH of 4 characterizes the cassava ethanol wastewater. A lab-scale anaerobic continuously stirred tank reactor (CSTR) was used under thermophilic condition (55degC) to treat cassava ethanol wastewater. Experimental results showed that successful start up of the reactor inoculated with mesophilic granular sludge could be obtained after 40 days continuous operation with step-wise increases in the organic loading rate. The organic loading rate could reach as high as 14 kgCOD/(m³-d) by decreasing the hydraulic retention time to 5 days. The performance of reactor was stable with TCOD removal efficiency of 90% and biogas production of 18L/d containing about 60% methane. Moreover, significant fluctuation in performance of reactor was not observed with the changes of organic loading rate. And results showed adjustment of pH or alkalinity is not necessary due to the sound buffer capacity of the system.